Microwave ovens are accepted by more and more families due to their convenience and quickness of heating and cooking food. In the related art, when food is heated in a microwave oven, the food is directly or (the food must be loaded in vessels) indirectly placed in a cavity and is evenly heated by microwaves. This microwave oven is liable to cause water loss of the food when the food is heated or reheated, resulting in that the heated food is quite dry and affecting the taste and the nutrition of the food.